US nuclear performance figures

American nuclear operators posted good performances last year with fewer unplanned shutdowns than any year since 2005 and strong capacity factors across the fleet.

Figures for nuclear operations in 2011 were compiled by the Institute of Nuclear Power Operators and revealed by US trade group the Nuclear Energy Institute (NEI).

There are 104 large nuclear reactors installed at power plants around the USA and these provided 790 billion units of electricity last year - enough to meet 19.2% of US needs. Across the whole fleet only 62 unplanned shutdowns were recorded in 2011, which the NEI said is three fewer than the previous record posted in 2005.

The Vermont Yankee nuclear power plant posted a capacity factor of over 90% last year

Tony Pietrangelo, senior vice president and chief nuclear officer at NEI, noted that the operational consistency came despite external events that can sometimes trigger shutdowns: Last year saw tornadoes in the southeast, a significant earthquake on the east coast and flooding in the midwest as well as Hurricane Irene.

Getting maintenance regimes right is key to successful nuclear power generation because it means a plant will be safe and proper to operate at full power without stopping at all between refuelling and maintenance outages that come every 12-18 months.

In line with this the US fleet posted two key metrics: a 91.4% capability factor (the proportion of the year that an average reactor was online and producing power); and an 89% capacity factor for the whole fleet (the amount of power produced as a percentage of the theoretical maximum).

The benefits of proper training, maintenance and oversight are also reflected in a good safety record: the NEI said that the rate of industrial accidents at US nuclear power plants was 0.06 per 200,000 hours worked - among the safest of any industry.